[sdiy] black flaky chip legs: what does this indicate?

[Shawn Rakestraw]

I found something like this on some transistors in an old reel to reel tape
deck from the late 60s. The legs were black and looked sort of oxidized
(like rust) but pure black. Not sure if that is the same as what you found
and no idea why either. I would like to hear the others weigh in though.

Shawn

On Sun, Nov 1, 2020, 5:14 PM S Ridley <spridley1 at gmail.com> wrote:

> Were the blackened legs on Texas chips?   I've seen a lot of this on ICs
> from the late 1970s or early 80s.
>
> I heard that Texas offered different grades of plating for ICs which were
> meant to be soldered or socketed - less plating on the ones which were
> meant to be soldered.  As these were cheaper...  well, guess the rest.
>  While I can't confirm the story is true, it ties in with what I've seen.
>
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> Steve
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> On Sun, 1 Nov 2020 at 19:21, Kenny Balys <kenny at beatkamp.com> wrote:
>
>>
>> I completed a repair and had two 74LS138's with blackened
>> legs. I went to pull one and it came apart. The legs are
>> degraded somehow. Then on to the other 74LS138: same.
>> The legs of the IC's just fell away.
>>
>> What could have caused this?
>> Has anyone seen something like this?
>>
>> There is no Varta battery pack on the board. I have seen
>> something like this on a Poly-Six.
>>
>> Other IC's near these two were not the same. The circuit
>> board seems to be ok.
>>
>> The instrument is now functional after replacing the
>> two 138's and changing a few caps.
>>
>> Thanks in advance for any ideas.
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